. From the experimental characterization of the hygrothermal properties of straw-clay mixtures to the numerical assessment of their buffering potential. Building and Environment, Elsevier, 2016, 97, pp.69 -81. 10.1016/j.buildenv.2015 1 From the experimental characterization of the hygrothermal properties of straw-clay mixtures to the numerical assessment of their buffering potential ABSTRACTThe development of innovative materials has to respond to both environmental and energy concerns. Bio-based materials are relevant because they are made from renewable raw materials and are carbon neutral. Similarly, unprocessed earth has a very low embodied energy. In this paper, the basic hygrothermal properties of straw-clay samples provided by two French companies were determined. Mixes with densities lower than 450 kg.m -3 would be suitable for use as self-insulating material in current construction. In addition, the material showed a high sorption capacity and very high water vapour permeability. The measurements were then implemented in a numerical model in order to simulate the hygric response of a small room. The straw-clay mixture was found to have a moisture buffering effect of the same magnitude as walls made of hemp concrete and largely higher than conventional walls. The influence of various indoor finishing materials was investigated through additional simulations.

For Heat, Air and Moisture modelling, one of the most crucial hygrothermal properties of porous construction materials is the sorption isotherm. Current techniques for measuring the sorption isotherm rely on the standardized Saturated Salt Solution (SSS) method which is known to be time consuming. Recently, a device called Dynamic Vapor Sorption was applied on building materials allowing faster measurements but limiting the mass and volume of the sample. As this technique is not yet standardized, an experimental procedure was developed and validated on barley straw. Results were also in good agreement with the measurements from the SSS technique.

Here we document the performance of a radiant cooling panel made of flow channels sandwiched between a suspended metal plate and an insulation layer. The flow passages represent the crucial element of the panel. In the present work, the heat transfer and flow characteristics of the panel are investigated. A numerical study is conducted to explore the role played by the flow architectures on the overall performance of the panel in steady state, subjected to radiation and convection heat fluxes from the bottom. A comparison between serpentine and canopy-to-canopy (dendritic) flow channels is presented. In all the cases, the following geometrical constrains apply: fixed plate area and flow volume. From one configuration to the other, the flow is given more freedom to morph in accord with the Constructal approach. We demonstrated that the dendritic architecture allows a significant improvement in the cooling panel performance, with more cooling capacity and less pumping power. In addition, we showed that the morphing of the panel itself toward more compactness is also a way to increase the ratio of cooling capacity/pumping power.

The influence of flow structures on the design of radiant cooling panel is explored  Serpentine and Constructal flow layouts are investigated  A numerical model is employed to evaluate the thermo-fluid performance of the panel  Branching flow arrangements have the potential of improving the global performances

Hydrogen gas was injected, together with helium and neon, into a borehole in the low-diffusivity Opalinus Clay rock. The hydrogen partial pressure was at most 60 mbar. A water production flow rate from the surrounding rock of c. 15 ml/day had been obtained previously, indicating that the test interval wall was presumably saturated with water. Helium and neon concentrations decreased as expected while taking into account dissolution and diffusion processes in the porewater. In contrast, the disappearance rate of hydrogen observed (2 × 10 24 to 3 × 10 24 mol/day/m 2 ) was c. 20 times larger than the calculated rate considering only dissolution and diffusion. The same rate was observed following a new hydrogen injection and over a six-month semi-continuous injection phase. Simultaneously, sulphate and iron concentrations decreased in the water, whereas sulphide became detectable. These evolutions may be due to biotic processes involving hydrogen oxidation, sulphate reduction and Fe(III) reduction.

The work documents the design of Earth-Air Heat Exchangers based not only on sensible heat transfer, but also on latent heat exchanges. We compare the impact of the climate of Brazil and south of France on the relevance of such systems. The duct length is determined in order to obtain maximum underground heat exchanges. A time dependent model combined to actual weather data is developed to show when an underground heat exchanger becomes a good option in a tropical climate. The three-dimensional version of the model accounts for heat transfer in the soil and for heat and moisture transfer along the underground pipe. The comparison with a 1D model allows to propose a straightforward approach to assess the cooling/heating potential of different climatic regions.

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Laboratory test to assess sensitivity of bio-based earth materials to fungal growth. (2018) Building and Environment, 142. 11-21.